4 ms·

* Sand is not a good substrate for plants. Too fine - aeration problems; surface to volume ratio not good. Anaerobic zones will form. Denitrification with odor

* Sand is not a good substrate for plants. Too fine - aeration problems; surface to volume ratio not good. Anaerobic zones will form. Denitrification with odor will stress plants and fishes. * No dedicated biofilter. Nitrification bacteria will form and live on the sand. Tight coupling between fsh tank and grow beds. No way to decouple when one or the other has to be maintained. * Fine mesh preventing the sand to get into the fish tank will clogg with detritus. * Grow beds will clogg with detritus after approximately one season. * No sump tank. Water level in the fish tank will vary a lot. Fish don't like that. Stocking density will have to be low to aleviate this. * Too much sun on the fish tank. Most fish species don't like this and algae will form rapidly. Please do not _sell_ aquaponic designs like this one. I'm doing aquaponics since 2012 and I'm currently working in aquaponic research for a university.

nkurz 10y ago
Sand is not a good substrate for plants. What's a better inexpensive substrate? I've been finding Diatomaceous Earth (sold as kitty litter or oil absorbent) to be great for starting seedlings, but it's more expensive than desirable for filling a large volume. Detailed thread here: http://www.tomatoville.com/showthread.php?t=22329 http://www.tomatoville.com/showthread.php?t=22329
- spiderfarmer 10y ago
  http://www.grodan.nl/oplossingen/groenteteelt+producten/grotop+master http://www.grodan.nl/oplossingen/groenteteelt+producten/grot... Used in Dutch greenhouses for the last 20 years or so.
  - jsilence 10y ago
    Most of the grodan producs are made from rock wool. From a plant perspective it is a very good substrate, good capilarity, inert, stable. But it is not compostable and recyclable. For a classical ebb and flow grow bed, the rock wool fibers are too fine grained.
    - spiderfarmer 10y ago
      You're wrong, it is 100% recyclable[1]. Otherwise we would have an enormous heap of those things. It's not composted, but luckily these things can be recycled into other, more useful products. You basically can't sell compost over here as there is too much compost already. We're already exporting compost to the UK for very low prices. [1] https://www.youtube.com/watch?v=f5yw_RIU59o https://www.youtube.com/watch?v=f5yw_RIU59o
      - jsilence 10y ago
        Ah cool, good to know. Thank you for the pointer.
- jsilence 10y ago
  For ebb and flow grow beds expanded clay (LECA) or three quarter inch gravel are proven to work well. Make sure beforehand that your substrate does not change pH. Cat litter stuff or Seramis is to finde grained for the grow beds.
ph0rque 10y ago
The sand-based system is based on Dr. McMurtry's aquaponics research at NC State University. Here are a list of publications about it: http://iavs.info/publications/ http://iavs.info/publications/ * In general, course sand is a great substrate for plants. Both research and my own experience show no problems with aeration or anaerobic zones forming. * The sand is the biofilter. This does form a tight coupling of the system, but does not prevent regular maintenance. For intensive maintenance, you would need to take the fish out of the fish tanks anyway. * No clogging has occurred so far because of the mesh. * What length of time is one season? What will happen after one season that won't happen after X days/weeks/months? * The water begins draining from the veggie beds seconds after the flooding cycle starts, so the water level in the fish tank only varies by ~10-15%. * How rapidly will the algae form? Two months later, I don't really see algae forming in the fish tank. There is algae growing in the furrows, but that's a good thing, since algae forms a natural nutrient battery. In any case, the fish tank placement is not optimal in my prototype, and can be improved in subsequent installations.
- jsilence 10y ago
  Thanks for the pointer to Dr McMurtys research. Will read. Sand might be a good substrate for hydroponics, but with aquaponics, especially when you are not removing the solids prior to flooding the beds, I doubt you will run the system at optimal performance. Regarding this and the clogging topic I'd like to know at what stocking density you have been running your systems. Our experience so far is that systems are easier to run stable with low stocking density and low feed intensity. This is a valid approach for home systems, but results in lower yields. When you start raising stocking density and feed intensity, the nutrient concentration becomes more attractive for the plants. But then solid removal becomes quite important. I am pretty sure if you simply pipe the aquaculture water into sand beds without prior processing, solids will accumulate in the grow beds. You're saying that you did not have any problems regarding aeration. Did you measure DO and nitrites? How does pH behave in your system? Does it drop, rise or stay constant? "What will happen after one season that won't happen after X days/weeks/months?" Experience from other researchers with ebb and flow show that even with gravel and LECA sludge builds up in the grow beds and that starting from the second season this can become a problem. Then the grow bed has to be dug out and cleaned from sludge. "How rapidly will the algae form?" We recently built a system (on customer request) that has a lot of light on the fish tank. Algae built up after two weeks. Massively. Again, low algea formation in your systems might be due to low stocking density. If the plants have a chance to consume the nutrients and therefore keep the nutrient concentrations low enough to prohibit algae growth, then it might appear ok. But then you are starving the plants, reducing yield.

nkurz 10y ago

Sand is not a good substrate for plants. What's a better inexpensive substrate? I've been finding Diatomaceous Earth (sold as kitty litter or oil absorbent) to be great for starting seedlings, but it's more expensive than desirable for filling a large volume. Detailed thread here: http://www.tomatoville.com/showthread.php?t=22329 http://www.tomatoville.com/showthread.php?t=22329

spiderfarmer 10y ago
http://www.grodan.nl/oplossingen/groenteteelt+producten/grotop+master http://www.grodan.nl/oplossingen/groenteteelt+producten/grot... Used in Dutch greenhouses for the last 20 years or so.
- jsilence 10y ago
  Most of the grodan producs are made from rock wool. From a plant perspective it is a very good substrate, good capilarity, inert, stable. But it is not compostable and recyclable. For a classical ebb and flow grow bed, the rock wool fibers are too fine grained.
  - spiderfarmer 10y ago
    You're wrong, it is 100% recyclable[1]. Otherwise we would have an enormous heap of those things. It's not composted, but luckily these things can be recycled into other, more useful products. You basically can't sell compost over here as there is too much compost already. We're already exporting compost to the UK for very low prices. [1] https://www.youtube.com/watch?v=f5yw_RIU59o https://www.youtube.com/watch?v=f5yw_RIU59o
    - jsilence 10y ago
      Ah cool, good to know. Thank you for the pointer.
jsilence 10y ago
For ebb and flow grow beds expanded clay (LECA) or three quarter inch gravel are proven to work well. Make sure beforehand that your substrate does not change pH. Cat litter stuff or Seramis is to finde grained for the grow beds.

ph0rque 10y ago

The sand-based system is based on Dr. McMurtry's aquaponics research at NC State University. Here are a list of publications about it: http://iavs.info/publications/ http://iavs.info/publications/ * In general, course sand is a great substrate for plants. Both research and my own experience show no problems with aeration or anaerobic zones forming. * The sand is the biofilter. This does form a tight coupling of the system, but does not prevent regular maintenance. For intensive maintenance, you would need to take the fish out of the fish tanks anyway. * No clogging has occurred so far because of the mesh. * What length of time is one season? What will happen after one season that won't happen after X days/weeks/months? * The water begins draining from the veggie beds seconds after the flooding cycle starts, so the water level in the fish tank only varies by ~10-15%. * How rapidly will the algae form? Two months later, I don't really see algae forming in the fish tank. There is algae growing in the furrows, but that's a good thing, since algae forms a natural nutrient battery. In any case, the fish tank placement is not optimal in my prototype, and can be improved in subsequent installations.

jsilence 10y ago
Thanks for the pointer to Dr McMurtys research. Will read. Sand might be a good substrate for hydroponics, but with aquaponics, especially when you are not removing the solids prior to flooding the beds, I doubt you will run the system at optimal performance. Regarding this and the clogging topic I'd like to know at what stocking density you have been running your systems. Our experience so far is that systems are easier to run stable with low stocking density and low feed intensity. This is a valid approach for home systems, but results in lower yields. When you start raising stocking density and feed intensity, the nutrient concentration becomes more attractive for the plants. But then solid removal becomes quite important. I am pretty sure if you simply pipe the aquaculture water into sand beds without prior processing, solids will accumulate in the grow beds. You're saying that you did not have any problems regarding aeration. Did you measure DO and nitrites? How does pH behave in your system? Does it drop, rise or stay constant? "What will happen after one season that won't happen after X days/weeks/months?" Experience from other researchers with ebb and flow show that even with gravel and LECA sludge builds up in the grow beds and that starting from the second season this can become a problem. Then the grow bed has to be dug out and cleaned from sludge. "How rapidly will the algae form?" We recently built a system (on customer request) that has a lot of light on the fish tank. Algae built up after two weeks. Massively. Again, low algea formation in your systems might be due to low stocking density. If the plants have a chance to consume the nutrients and therefore keep the nutrient concentrations low enough to prohibit algae growth, then it might appear ok. But then you are starving the plants, reducing yield.